Time-activity patterns relationships

Exposure patterns, which usually reflect the time (e.g., hours day, days per calendar year) and location (e.g., geographical, microenvironment) relationship between sources of exposure (e.g., motor vehicles, home appliances, consumer products, and drinking water) and human activity patterns. Human activity patterns include where and how much time people spend in defined microenvironments during a given day. Further, it can be important to characterize their specific microactivities within a given microenvironment, e.g., the frequency of a 1-2-year-old child s hand-to-mouth... 

The relation between tissue injury and the appearance of enzymes in the circulation is most clearly seen in the condition of myocardial infarction, in which a relatively short episode of damage is followed by a rapid transfer of enzymes to the circulatory system. About 24 hours after a myocardial infarction, the pattern of relative activity of various enzymes in the circulatory system closely resembles that in the myocardial tissue. These relationships are less clearly recognized in other conditions, such as chronic liver disease, in which enzyme release is a process that continues for a period of time. The pattern of relative enzyme activities in serum in chronic disease may also become distorted by differential rates of removal of enzymes from the circulation and possibly also by differential changes of rates of enzyme synthesis in the affected tissue. 

Flavonoids, especially flavones and flavonols, also directly bind to several CYP isoforms (lAl, 1A2, IBl, 3A4) involved in xenobiotics metabolism and inhibit enzyme activity. Structure-activity relationships show rather high isoform selectivities depending on the flavonoid substitution pattern and contrasted inhibition mechanisms. For instance, inhibition by flavonoids of 7-methoxyresorufin O-demethylation in microsomes enriched in CYP lAl and 1A2 reveals that galangin (3,5,7-trihydroxyflavone) is a mixed inhibitor of CYP 1A2 (.ST = 8 nM) and a five times less potent inhibitor of CYP 1A1. By contrast, 7-hydroxy flavone is a competitive inhibitor of CYP lAl (Aii = 15 nM) and a six times less potent inhibitor of CYP 1A2. In addition, fairly selective inhibition of CYP IBl (specifically detected in cancer cells) by some flavonoids has been reported. For example, 5,7-dihydroxy-4 -methoxyflavone inhibits IBl, 1 Al, and 1A2 with IC50 values of 7, 80, and 80 nM, respectively. ... 

Pomin and Mourao, 2008 Vilela-Silva et ah, 2008). This is of enormous benefit to the entire field of glycobiology. At one time, it was relatively hard to accurately correlate the structure-activity relationship for the majority of SPs. This same advantage is also observed for some marine invertebrate GAGs (Fig. 12.2F). In contrast, many mammalian GAGs exhibit a large variety of sulfation patterns (Gandhi and Mancera, 2008) and consequentially demand much more effort to assay their biological activities, determine their specific structural features, and subsequently propose a dependable structure-function relationship. 

Pharmacokinetic information that relates blood concentration to toxic response is critical in defining such dose-response relationships, but information on peak blood concentrations or blood concentrations over time (area under the curve (AUC)) is seldom available. One agent for which such information has been published is 2-methoxyacetic acid (2-MAA), the active metabolite of 2-methoxyethanol. Terry et al. (1994) showed that peak concentration was related to neural tube defects observed after exposure in mice on gestation day 8, whereas area under the curve was shown to be related to limb defects after exposure to 2-MAA on gestation day 11 (Clarke et al. 1992), suggesting that the time of exposure and pattern of development of the susceptible organ... 

Further evidence has been presented that a strong association exists between smoking and atherosclerosis. Increased mortality is seen in smokers j although the correlation between smoking and serum lipid patterns is not clear. A study by the Health Insurance Plan of Greater New York has shown that physical activity plays a role. The least active smoker has an incidence of rapidly fatal myocardial Infarction which is nine times that found among the most active smokers. A rapid rise in free fatty acid is seen and an enhanced utilization of fatty acids occurs in smokers apparently due to nicotine ingestion. The relationship of this fatty acid rise to myocardial infarction is uncertain. 

By using a trained SOM, bonds in a molecule are mapped into the SOM and the pattern of activated neurons is interpreted as a fingerprint of the bonds of the molecule. For numerical processing, each neuron is assigned a value equal to the number of times it was activated by bonds of the molecule. The map, that is, a matrix, is then transformed into a vector by concatenation of columns. This vector is called MOLMAP descriptor. To account for proximity relationship, a value of 0.3 is added to each neuron multiplied by the number of times a neighbor was activated by a bond. 

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